Recently, due to the exhaustion of fossil energy and environmental pollution, the interest in electric products, which may operate with electric energy instead of fossil energy, is growing more and more.
Accordingly, with the increasing development of mobile devices, electric vehicles, hybrid vehicles, power storage devices, uninterrupted power supplies, or the like, the consumption of secondary batteries as energy sources are rapidly increasing as well as its various forms. Therefore, secondary batteries are being studied very actively to cope with such diverse demands.
Meanwhile, a device using a high-power large-capacity secondary battery, such as an electric vehicle or a hybrid vehicle, needs to maintain good isolation between the device and the secondary battery. If not, bad isolation of the secondary battery brings a leakage current, which causes various problems. For reference, a leakage current causes an unexpected discharge of the secondary battery or malfunctions of electronic components included in the device. In addition, in case of a device using a high voltage battery, such as an electric vehicle, a leakage current may give a fatal electric shock to a person.
In order to solve problems caused by such a leakage current, various kinds of isolation resistance measuring devices for determining an isolation state of a secondary battery are being developed and used. However, if a fault occurs at the isolation resistance measuring apparatus so that an isolation resistance value is not accurately calculated, the advantageous effects of the device deteriorates and it is not possible to solve various problems caused by a leakage current. Therefore, there is an additional demand for a function of self-diagnosing a fault of an isolation resistance measuring apparatus.